Forming an eye end termination on a rope

ABSTRACT

There is disclosed a method of forming an eye end termination on a rope having a core comprising a plurality of multi-strand subropes, and a rope having a core comprising a plurality of multi-strand subropes and at least one eye end termination. In one embodiment, a method of forming an eye end termination ( 16 ) on a rope ( 10 ) having a core ( 12 ) is disclosed. The rope comprises a plurality of multi-strand subropes ( 14 ) each of a first strength, and the method comprising the steps of: coupling a pair of subropes ( 14 ) in the rope core ( 12 ) together using a multi-strand coupling rope ( 18 ) of a second strength which is greater than said first strength, to thereby form at least part of the eye end termination ( 16 ). The step of coupling the pair of subropes ( 14 ) together comprises splicing a first portion of a coupling rope ( 18 ) to one of the subropes in the pair of subropes, and splicing a second portion of the coupling rope to the other one of the subropes in the pair of subropes.

The present invention relates to a method of forming an eye end termination on a rope having a core comprising a plurality of multi-strand subropes. The present invention also relates to a rope having a core comprising a plurality of multi-strand subropes and at least one eye end termination. In particular, but not exclusively, the present invention relates to a method of forming an eye end termination on such a rope involving coupling at least one pair of sub ropes in the rope core together.

In the oil and gas exploration and production industry, the search for oil and gas offshore is moving into deeper and deeper waters and will continue to do so. Traditionally, in shallower waters, drilling and production vessels have been moored to the seabed using chain and wire. However, in deeper waters there is a drive to moor these vessels with synthetic fibre ropes, as they can offer many advantages such as reduced platform offset, reduced peak loads and increased payload capacity.

Due to limitations in manufacturing and handling of synthetic fibre ropes, individual mooring lines for a vessel are normally split into a number of rope sections. The conventional method to connect the rope sections together is to mount a steel spool inside an eye end termination on each rope section. The steel spools are then attached to each end of a small length of chain using shackles, so that the rope sections can be coupled together. Alternatively an “H-link” connector may be utilised.

However, as the requirement for break load is increasing, the size and weight of connecting components is also increasing. This not only makes the rope sections difficult to handle and connect, it can also have an affect on the dynamics of a mooring system comprising such mooring lines. In particular, studies have shown that the weight of the connecting components (spools plus shackles and chains, H-link connectors) between fibre rope sections in a mooring line can affect the performance of the mooring system. This is because the weight of these components creates a catenary in the line, giving a lower initial stiffness. As the load in the line increases, the line becomes taut and the stiffness increases. This lower initial stiffness is undesirable, as it allows a greater offset of the vessel. In other words, the vessel can move a significant distance before the line becomes taut and further movement is effectively resisted.

One known type of fibre rope is a polyester rope that is produced with a central core surrounded by a layer of filter fabric encased in a braided jacket. The core is the load-bearing part of the rope, and is constructed from a number of multi-strand (typically three-strand) polyester subropes laid parallel to each other. The subropes are each typically constructed from a number of yarns, which are long lengths of continuous interlocked fibres. The subropes are usually arranged in outwardly radiating rope arrays or layers. There is no set arrangement for the subropes in the core, as it is very difficult to maintain the subropes in an exact position during manufacture. Typically the aim is to have a pattern of subropes which is ideally increased by six for each concentric array of subropes, although the total number of subropes in the core is selected so as to be divisible by four (for reasons that will be discussed below) and so the number of subropes in the outer array adjusted accordingly. For example, the rope may have a first array of three subropes, a second array of nine subropes around the first array and a third array of twelve subropes around the second array (thus a 3-9-12 pattern giving a total of 24 subropes). The number of subropes in the core also depends upon other factors including the desired length of the rope. Other arrangements are possible depending on the particular rope structure required.

Typically, the number of subropes ranges between twelve and eighty, depending on factors including the minimum breaking load (the ‘MBL’ or failing load) and length of the segments. Half of the subropes are ‘S’ lay (wound clockwise) and half are ‘Z’ lay (wound anti/counter-clockwise), resulting in a torque neutral rope. A torque neutral rope is one in which no twist or torque is generated from the rope when loaded. The core of subropes is wrapped in the layer of filter fabric, which is used to restrict ingress of particles into the core that might otherwise abrade and damage the rope during use. The outer braided jacket holds the structure of the rope together, and protects the subropes and filter from abrasion damage. A drawing of the end of one such known rope 1, having a core 2 comprising subropes 3, is shown in the perspective view of Fig. A. Parts of a filter layer 4 and braided jacket 5 of the rope 1 have been removed, and some of the subropes 3 shown longer than others, for illustration purposes. Other ropes may be of a similar construction but with different arrangements of subropes. For example, in certain circumstances, it may not be desired or required to have a torque neutral rope, and so the subropes may not be arranged so that half are S lay and half Z lay.

The current method of forming an eye end termination in ropes of this kind involves an eye-splicing procedure. The splice is built up using a number of layers, and the method is shown in the schematic plan views of Figs. B and C. An eye end termination 6 (Fig. B) is formed around a bollard 7 and starts with subropes 8 and 9. These are laid either side of the bollard 7, and marked with points ‘a’ and ‘b’. The subropes 8 and 9 are then passed around the bollard 7, and the ‘a’ and ‘b’ marks are lined up on each side. Subrope 8 is then spliced into subrope 9, and visa versa, using an eye splice in which individual strands of the subropes are tucked or plaited together. This completes one pair of subropes 8 and 9. The distance between the ‘a’ and ‘b’ marks is determined according to the diameter of the bollard, the diameter of the subropes, the extension of the subrope under load and the bedding down of the subropes around the eye when the rope is loaded. The aim is to have all the subropes at the same length at break load for maximum strength.

The process is then repeated depending on how many subropes are required in a first layer of the eye end termination 6. The process is then repeated for subropes in a second layer of the eye end termination 6, as shown in Fig. C with subropes 8′ and 9′. In this case however, the ‘b’ marks are changed to ‘c’ marks. This is because the rope portions between the ‘a’ and ‘c’ marks are slightly longer than between the ‘a’ and t′marks, to account for the extra distance around a perimeter of the eye 6 that the subropes 8′ and 9′ must pass (due to the increased dimension of the eye which results from forming of the first layer of subropes). The splice is thus built up in layers, governed by factors including the desired number of subropes in each layer and the particular design of the rope 1. Typically there are four subropes in each layer, hence the total number of subropes in the core 2 will be divisible by four.

Once all of the subropes in the core 2 have been spliced, a braided cover (not shown) is fitted over the spliced regions and around the eye 6. This is secured in position by tucking yarns of the braided cover into the cover plaits of the standing rope. Typically, the cover yarns are locked in place by completing four tucks of the ropes in the eye end termination into the cover plaits. Using a special tool known as a ‘fid’, the eye end termination yarns are pushed under one plait of the cover and then over another plait, and this process is repeated four times to provide the required engagement. To finish, the eye 6 and spliced regions are coated with a two part polyurethane coating to provide abrasion resistance during handling, as shown in Fig. D.

Whilst this known technique provides a good eye end termination capable of supporting the loads experienced by the rope during use, the splicing process results in the eye end termination being relatively bulky. This is because the process of passing each rope in a pair of subropes that are to be spliced together around the bollard results in there being 200% of the rope core material in the eye end termination and in the spliced region (each leg of the eye end termination comprising the same number of ropes as in the rope core, and thus effectively each comprising 100% of the rope core material). Consequently, the eye end termination is larger than might otherwise be the case for a rope of particular dimensions and with a certain number of core subropes. As a result of this, the spool which is fitted into the eye is larger than might otherwise be necessary, adding to the weight of connecting components in a mooring line constructed from such rope sections, and thus enhancing catenary effects. Similar problems are experienced when utilising H-link connectors.

It is amongst the objects of the present invention to obviate or mitigate at least one of the foregoing disadvantages.

According to a first aspect of the present invention, there is provided a method of forming an eye end termination on a rope having a core comprising a plurality of multi-strand subropes, the method comprising the step of:

-   -   coupling a pair of subropes in the rope core together using a         multi-strand coupling rope, to thereby form at least part of an         eye end termination;     -   wherein the step of coupling the pair of subropes together         comprises splicing a first portion of the coupling rope to one         of the subropes in the pair of subropes, and         splicing a second portion of the coupling rope to the other one         of the subropes in the pair of subropes.

The invention may provide a method of forming an eye end termination in which the requirement to have two subropes passing around a perimeter of the eye end termination and directly spliced together can be negated. This may facilitate a reduction in the size of the eye end termination compared to prior rope eye end terminations, with the result that a spool fitted in the eye end termination can be of a reduced size and weight in comparison to prior spools for ropes of similar dimensions, materials and/or load bearing characteristics. This can lead to a reduction in catenary effects in the rope, and thus in a mooring line comprising a plurality of sections of such rope coupled together end-to-end. Reductions in the spool weight of up to 50% may be achievable. A further benefit is that the spool and associated connecting equipment is significantly lighter than with prior ropes and so easier to handle, which increases safety offshore during installation.

The method may be a method of forming an eye end termination on a rope, in which the number of coupling ropes extending around a perimeter of and forming at least part of the eye end termination is less than the number of subropes in the rope core, and which may be half the number of subropes in the core.

The plurality of multi-strand subropes may each be of a first strength, and the step of coupling the pair of subropes together may comprise coupling the pair of subropes together using a coupling rope which is of a second strength which is greater than said first strength. The method may therefore involve the coupling together of the subropes in the pair using a coupling rope which is of a greater strength than that of the subropes. In this way, the coupling rope forming at least part of the eye end termination is capable of supporting higher loading than the core subropes, and so any reduction in strength of the eye end termination which might otherwise result from the reduction in the number of ropes in/forming the eye end termination can be negated. Indeed, depending upon the relative first and second strengths of the subropes and the coupling rope, the eye end termination may be capable of supporting the same (or indeed greater) loading than a conventional eye end termination formed on the same rope following the prior technique described above. There may be a plurality of coupling ropes, each of said second strength.

The first portion of the coupling rope may be spaced along a length of the coupling rope from the second portion. The first portion of the coupling rope may be or may comprise a first end of the coupling rope. The second portion of the coupling rope may be or may comprise a second end of the coupling rope.

The coupling of the pair of subropes together using the coupling rope may involve forming a loop comprising the coupling rope and parts of the first and second subropes in the subrope pair to which the coupling rope is spliced, which loop may form at least part of the eye end termination.

The method may comprise the steps of:

-   -   coupling a first pair of subropes in the rope core together         using a first multi-strand coupling rope, to thereby form part         of an eye end termination; and     -   coupling at least one further pair of subropes in the rope core         together using at least one further multi-strand coupling rope,         to thereby form a further part of the eye end termination.

The step of coupling the first pair of subropes together may comprise splicing a first portion of the first coupling rope to one of the subropes in the first pair of subropes, and splicing a second portion of the first coupling rope to the other one of the subropes in the first pair of subropes. The step of coupling the at least one further pair of subropes together may comprise splicing a first portion of the at least one further coupling rope to one of the subropes in the at least one further pair of subropes, and splicing a second portion of the at least one further coupling rope to the other one of the subropes in the at least one further pair of subropes.

The rope core may comprise a plurality of concentric arrays or layers of subropes. The rope core may comprise a first array of subropes, and at least one further array of subropes, the or each said further array of subropes located radially outwardly of the or each preceding array. For example, the rope core may comprise a first array of subropes, a second array of subropes located around the first array of subropes, and a third array of subropes located around the second array of subropes.

The method may comprise the steps of:

-   -   coupling a pair of subropes in a first array of the rope core         together using a first multi-strand coupling rope, to thereby         form part of an eye end termination; and     -   coupling a pair of subropes in at least one further array of the         rope core together using at least one further multi-strand         coupling rope, to thereby form a further part of the eye end         termination.

The step of coupling the pair of subropes in the first rope core array together may comprise splicing a first portion of the first coupling rope to one of the subropes in said pair of subropes, and splicing a second portion of the first coupling rope to the other one of the subropes in said pair of subropes. The step of coupling the pair of subropes in the at least one further array together may comprise splicing a first portion of the at least one further coupling rope to one of the subropes in said pair of subropes, and splicing a second portion of the at least one further coupling rope to the other one of the subropes in said pair of subropes.

One or more of the arrays of subropes in the rope core may comprise a plurality of pairs of subropes, and the method may comprise the steps of:

-   -   coupling a first pair of subropes in at least one of the arrays         of the rope core together using a first multi-strand coupling         rope, to thereby form part of an eye end termination; and     -   coupling at least one further pair of subropes in said array of         the rope core together using at least one further multi-strand         coupling rope, to thereby form a further part of the eye end         termination.

The step of coupling the first pair of subropes in said array together may comprise splicing a first portion of the first coupling rope to one of the subropes in the first pair of subropes, and splicing a second portion of the first coupling rope to the other one of the subropes in the first pair of subropes. The step of coupling the at least one further pair of subropes in said array together may comprise splicing a first portion of the at least one further coupling rope to one of the subropes in the at least one further pair of subropes, and splicing a second portion of the at least one further coupling rope to the other one of the subropes in the at least one further pair of subropes.

The method may comprise coupling a subrope in one array of the rope core to a subrope in another array of the rope core using a coupling rope.

The method may comprise coupling each subrope in the rope core to another subrope in the core using a coupling rope.

The method may comprise coupling a plurality of pairs of subropes of the rope core together using respective coupling ropes, and arranging the coupling ropes to form overlapping rope layers of the eye end termination. The method may comprise coupling at least two pairs of subropes in the rope core together using respective coupling ropes and arranging said coupling ropes in a first layer; and coupling at least two further pairs of subropes in the rope core together using respective further coupling ropes and arranging said coupling ropes in a second layer located around the first layer. The method may comprise coupling at least two still further pairs of subropes in the rope core together using respective still further coupling ropes and arranging said coupling ropes in a third layer located around the second layer. Further layers may be created if required.

The method may comprise forming each layer from four coupling ropes (or multiples thereof) and thus may comprise coupling four pairs of subropes in the rope core together. This may facilitate the balancing of forces in the eye end termination. For example, the rope may be torque balanced and the rope core may comprise a number of S lay subropes and a corresponding number of Z lay subropes. The method may comprise coupling pairs of S lay subropes together using S lay coupling ropes, and coupling pairs of Z lay subropes together using Z lay coupling ropes. The provision of four coupling ropes in each layer may facilitate balancing of forces in the eye end termination in that an even number of S lay coupling ropes can be provided in each layer, and a corresponding even number of Z lay coupling ropes. Each layer may comprise an even number of coupling ropes, may comprise more than four coupling ropes and, in such circumstances, may comprise coupling ropes arranged in multiples of four.

The method may be a method of forming an eye end termination having at least two separate loops or eyes. This may provide the advantage that two ropes or rope sections may be coupled together using a single connecting component or connecting assembly, which may be a single spool. In particular, a rope with an eye end termination having two loops can be coupled to a spool straddling the loop or loops of an eye end termination of a further rope. In this way, forces on the spool during use can be balanced in a way which would not be possible with conventional eye end terminations. For example, two ropes with conventional eye end terminations could not be coupled together side by side on a spool, as there would be an imbalance in the forces acting on the spool tending to cause a twisting of the spool, and separation of the eye end terminations from the spool. The invention may therefore negate the requirement to provide a spool on each rope and a connecting chain coupling the spools together, or a relatively large and heavy H-link connector. Accordingly, the weight of a connecting component or assembly used to couple two such ropes together can be reduced, with resultant benefits including a reduced catenary in the rope.

The method may comprise the steps of:

-   -   coupling at least one pair of subropes in the rope core together         using a multi-strand coupling rope to thereby form at least part         of a first loop of the eye end termination; and     -   coupling at least one further pair of subropes in the rope core         together using a multi-strand coupling rope to thereby form at         least part of a further loop of the eye end termination, said         further loop being separate from the first loop.

The method may comprise the steps of:

-   -   coupling at least one pair of subropes in the rope core together         using a multi-strand coupling rope to thereby form at least part         of a first loop of the eye end termination;     -   coupling at least one further pair of subropes in the rope core         together using a multi-strand coupling rope to thereby form at         least part of a second loop of the eye end termination, the         second loop being separate from the first loop; and     -   coupling at least one still further pair of subropes in the rope         core together using a multi-strand coupling rope to thereby form         at least part of a further loop of the eye end termination, the         further loop being separate from the first and second loops.

Typically the eye end termination comprises two loops, although it may comprise more than two loops if desired. Limiting factors on the number of loops may be relative dimensions of the rope or eye end termination and/or the balancing of forces on a connecting component (such as a spool) used to couple the rope to another rope. Typically the eye end termination comprises an even number of loops. This may facilitate the balancing of forces on a connecting component used to couple two ropes together. However, the eye end termination may comprise an odd number of loops.

Each loop of the eye end termination may be formed by coupling at least one pair of subropes in the rope core together using a respective multi-strand coupling rope. Each loop may be formed by coupling a plurality of pairs of subropes in the rope core together using respective multi-strand coupling ropes. The ropes in each loop may be grouped together to form the loop, and may be secured together. The ropes may be secured together using at least one cover or the like fitted around the ropes in the group. A separate cover may be provided for each group of ropes. The method may comprise providing each loop of the eye end termination with a respective cover.

Each loop of the eye end termination may be formed according to the method(s) set out above. Thus further features in the step or steps of forming each loop may be derived from the text set out above.

According to a second aspect of the present invention, there is provided a rope comprising a core having a plurality of multi-strand subropes and at least one eye end termination;

-   -   wherein the eye end termination comprises at least one         multi-strand coupling rope having a first portion spliced to one         of a pair of subropes in the rope core and a second portion         spliced to the other one of the subropes in the pair of         subropes.

The subropes may each be of a first strength and the coupling rope of a second strength which is greater than said first strength.

The subropes may be of a polymeric material or materials. The subropes may be of a polyester material, a polyamide or nylon material which may be a common nylon material, or a combination thereof. The subrope strands may each comprise at least one yarn, each yarn being made up from a plurality of fibres; thus the subrope strands may themselves be multi-stranded. A strength of the material used to form the subropes may be less than a strength of a material used to form the coupling ropes.

The coupling ropes may be of a polymeric material. The coupling rope strands may each comprise at least one yarn, each yarn being made up from a plurality of fibres; thus the coupling rope strands may themselves be multi-stranded. The coupling ropes may be manufactured using a high performance yarn. The coupling ropes may have a second strength which is at least 1.5 times greater, may be at least 2.0 times greater, and may be at least 2.5 times greater than the first strength of the subropes. The coupling ropes may be of a second strength which is no more than 3.5 times greater, and which may be no more than 3.0 times greater than the first strength of the subropes. The coupling ropes may be of or may comprise an aromatic polyamide (Aramid) material, such as those commercially available under the Trade Marks KEVLAR, TWARON and TECHNORA. The coupling ropes may be of or may comprise a liquid crystal polymer material, such as those commercially available under the Trade Mark VECTRAN. The coupling ropes may be or may comprise a plurality of materials selected from the above group. For example, one or more strand of the coupling rope may be may of a material which is different to one or more other strand of the coupling rope. A strength of the material or materials used to form the coupling rope may be greater than the strength of the material forming the subropes.

Reference is made herein to a strength of the subropes and of the coupling rope. Such references may be to the ability of the subropes and the coupling ropes, and/or of the respective materials forming the subropes and the coupling ropes, to withstand an applied stress without failure. The strength may be a yield strength and/or an ultimate strength of the ropes. The strength may be the tenacity of fibres or yarn materials used to form the subropes and the coupling rope, which may be defined as the ultimate (breaking) strength of the fibre or fibres forming the respective rope divided by the linear mass density of said fibre or fibres. The tenacity of the material forming the coupling rope may be at least about 1900 mN/tex, at least about 2000 mN/tex, at least about 2100 mN/tex, at least about 2200 mN/tex, at least about 2300 mN/tex, or at least about 2400 mN/tex. The tenacity of the material forming the coupling rope may be no more than about 2500 mN/tex, no more than about 2600 mN/tex, or no more than about 2700 mN/tex. The tenacity of the material forming each of the subropes may be no more than about 800 mN/tex and may be no more than about 900 mN/tex.

The subropes may each have an MBL of at least about 300 kN, and the or each coupling rope may have an MBL of at least about 600 kN.

The eye end termination may comprise a first loop formed by coupling at least one pair of subropes in the rope core together using a multi-strand coupling rope; a second loop formed by coupling at least one further pair of subropes in the rope core together using a multi-strand coupling rope, the second loop being separate from the first loop; and at least one further loop formed by coupling at least one still further pair of subropes in the rope core together using a multi-strand coupling rope, the further loop being separate from the first and second loops.

The eye end termination may comprise at least two separate loops or eyes. Typically the eye end termination comprises two loops, although it may comprise more than two loops if desired. Typically the eye end termination comprises an even number of loops. However, the eye end termination may comprise an odd number of loops.

Each loop of the eye end termination may comprise a plurality of pairs of subropes of the rope core coupled together using respective multi-strand coupling ropes.

The ropes in each loop may be grouped together to form the loop, and may be secured together. The ropes may be secured together using at least one cover or the like fitted around the ropes in the group. A separate cover may be provided for each group of ropes. The method may comprise providing each loop of the eye end termination with a respective cover.

Further features of the rope of the second aspect of the present invention may be derived from or in relation to the method of the first aspect of the invention and/or are defined in the appended claims. Where the eye end termination of the rope comprises a plurality of loops, each loop may be formed according to the method(s) set out above. Thus further features of each loop may be derived from the text set out above in or with respect to the first aspect of the invention.

According to a third aspect of the present invention, there is provided an eye end termination for a rope comprising a core having a plurality of multi-strand subropes, the eye end termination comprising at least one multi-strand coupling rope having a first portion spliced to one of a pair of subropes in the rope core and a second portion spliced to the other one of the subropes in the pair of subropes.

Further features of the eye end termination of the third aspect of the present invention may be derived from or in relation to the method of the first aspect of the invention or the rope of the second aspect of the invention.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a side view of an end of a rope comprising a core having a plurality of multi-strand subropes similar to that shown in Fig. A, the rope comprising at least one eye end termination formed in accordance with a method of an embodiment of the present invention;

FIG. 1A is a cross-sectional view of the core of the rope shown in FIG. 1;

FIGS. 2, 3 and 4 are cross-sectional views taken in the direction of the arrows X-X, Y-Y and Z-Z, respectively, of the rope shown in FIG. 1;

FIGS. 5 and 6 are schematic illustrations of steps in the method of forming an eye end termination on the rope shown in FIG. 1;

FIGS. 7, 8 and 9 are side, plan and perspective views, respectively, of two ropes coupled together, each rope comprising a core having a plurality of multi-strand subropes similar to that shown in Fig. A and at least one eye end termination having a plurality of loops, the eye end terminations formed in accordance with a method of another embodiment of the present invention;

FIG. 10 is a side view of an end of one of the ropes shown in FIG. 7;

FIGS. 11, 12 and 13 are cross-sectional views taken in the direction of the arrows X′-X′, Y′-Y′ and Z′-Z′, respectively, of the rope shown in FIG. 10; and

FIGS. 14 and 15 are enlarged perspective and front views, respectively, of a connecting component in the form of a spool used to connect the ropes of FIGS. 7 to 9 together.

Turning firstly to FIG. 1, there is shown a plan view of an end part of a rope in accordance with an embodiment of the present invention, the rope indicated generally by reference numeral 10. The rope comprises a core 12 having a plurality of multi-strand subropes which are best shown in the cross-sectional view of FIG. 1A, and which are indicated generally by reference numeral 14. The subropes 14 each have three strands and are constructed from a number of yarns (comprising interlocked fibres). The number of yarns per strand can vary but, due to machine limitations, the maximum number of yarns has been found to be twenty-eight. The core 12 of the rope 10 is of a structure which is similar to the rope 1 shown in Fig. A, and thus includes a filter layer 13 and a braided outer jacket 15. To form the filter layer 13, an elongate strip of filter material (not shown) is helically wound onto the assembled core 12. A winding machine is used which helically winds the filter material around the subropes before the cover 15 is braided on top. The pitch of the helical wind is typically set to be half of the material width of the strip, so that there is a double layer of filter material over the rope core 12. Alternatively, the filter layer 13 is provided as a number of overlapping elongate longitudinally oriented strips. In this case, four strips of filter material are located at twelve, three, six and nine o'clock positions around the subropes before the cover braiding is applied. The braided jacket 15 is formed by braiding the jacket material around the formed filter layer. FIG. 1 also shows an eye end termination 16 formed on the rope 10 according to a method of the present invention. The cover yarns (not shown) of the braided jacket 15 are locked in place by completing four tucks of ropes in the eye end termination 16 into the cover plaits, in a known fashion.

FIG. 2 is a cross-sectional view of the subropes 14 in the end part shown in FIG. 1, and is taken in the direction of the arrows X-X. FIG. 2 shows the subropes 14 after separation from the core 12 and formation into a rectangular arrangement, which follows coupling. As explained above, the core may have one of many different arrangements of subropes 14. The end part of the rope 10 is also shown in the cross-sectional view of FIGS. 3 and 4, which are taken in the direction of the arrows Y-Y and Z-Z of FIG. 1.

The method of forming the eye end termination 16, and the rope 10 and eye end termination itself, will now be described with reference also to FIGS. 5 and 6, which are schematic plan views illustrating steps in the method. FIG. 5 shows an end 20 of the rope 10, and illustrates a pair 22 of subropes 14 a and 14 b. Each subrope 14 in the rope core 12 is of a similar structure, and where individual ropes are referred to they will be given the reference numeral 14 together with the suffix a, b, c etc. Also shown in FIG. 5 is a multi-strand coupling rope 18 a. Again, each multi-strand coupling rope 18 is of a similar structure, and where individual ropes are referred to they will be given the reference numeral 18 together with the suffix a, b, c etc. The coupling ropes 18 are also three-strand and, in a similar way to the subropes, are constructed from a number of yarns.

The subropes 14 in the core 12 are first separated out from the filter layer 13 and outer jacket 15 and labelled with their intended position in the finished eye end termination 16. The pair 22 of subropes 14 a, 14 b are separated out from the other subropes in preparation for coupling together using the coupling rope 18 a. This is achieved by splicing a first portion 26 a of the coupling rope 18 a to the subrope 14 a, and a second portion 28 a of the coupling rope 18 a to the subrope 14 b. The subropes 14 a, 14 b are shown prior to splicing in the left hand side of FIG. 5, and following splicing in the right hand side of FIG. 5.

The subropes 14 a, 14 b and indeed the remaining subropes in the core 12 have a first strength, and the coupling rope 18 a and indeed further coupling ropes of the eye end termination 16 have a second strength. The second strength is greater than the first strength, which accounts for the high forces which the eye end termination 16 will experience in use. A typical polyester subrope 14 may have an MBL of 300 kN and a typical coupling rope 18 of a high performance yarn may have an MBL of 600 kN.

The subropes 14 and coupling ropes 18 do not have to be of the same structure, but are of the same diameter to facilitate the splicing procedure. The subropes are of a polymeric material, typically a polyester such as 132000 dtex polyester yarn, or a polyamide which can be a common nylon. The coupling ropes 18 are manufactured using a high performance yarn. Suitable materials include aromatic polyamide (Aramid) materials, such as those commercially available under the Trade Marks KEVLAR, TWARON and TECHNORA and liquid crystal polymer materials, such as those commercially available under the Trade Mark VECTRAN. Typically the coupling ropes 18 have a second strength which is in the range of 1.5 to 3.0 times greater than the first strength of the subropes 14. The yarns forming the coupling ropes 18 may be of a material having a tenacity or ultimate (breaking) strength in the range of about 1900 mN/tex to about 2700 mN/tex. Yarns forming the subropes 14 in contrast may be of a material having a tenacity or ultimate (breaking) strength in the range of about 800 mN/tex to about 900 mN/tex; for example, a typical polyester material has a tenacity of around 870 mN/tex. Suitable materials for the yarns used to form the coupling and subropes 18 and 14 and having such tenacities include those listed above.

The method of forming the eye end termination 16 contrasts with prior methods in that the eye end termination is smaller than prior terminations formed on ropes having cores of similar dimensions and arrangement to the rope core 12. This facilitates use of a smaller spool (not shown), which is located in an eye aperture 29 which is formed when the subropes are coupled together. In particular, with prior eye end terminations such as the termination 6 shown in Figs. B, C and D, the pair of subropes 8 and 9 are directly spliced together and pass around the perimeter of the eye end termination. This results in twice the amount of rope material existing in both the eye and the spliced regions. In contrast, in the rope 10 of the present invention, there is the same total amount of material in the eye end connection 16 (across a cross-section of the entire eye end termination) as in the rope core 12. This can clearly be seen by comparing FIG. 2, which shows all of the subropes 14 in the core 12, and FIG. 3, which shows the coupling ropes 18 in a left leg 30 of the eye end termination 16 (a right leg 32 being of similar structure). The method of forming the eye end termination 16 and the rope 10 of the present invention will now be described in more detail.

As shown in the cross-sectional view of FIG. 1A, the rope 10 comprises first, second and third radial arrays of subropes 34, 35 and 36. The number of subropes in the core 12 will depend upon factors including the overall length of the rope 10 and the number of the layers in the eye end termination 16. In the illustrated embodiment, the first array 34 comprises three subropes 14, the second array 35 comprises nine subropes and the third array 36 comprises twelve subropes. This makes a total of twenty-four subropes 14 in the rope core 12. As will be explained below, the total number of subropes will be divisible by four, and typically in the range of twelve to eighty. During formation of the eye end termination 16, two of the subropes 14 in the first array 34 are coupled together whilst the third subrope 14 is coupled to one of the ropes in the second array 35, each pair of subropes coupled together using a multi-strand coupling rope 18 according to the technique shown in FIG. 5. FIG. 1A shows the two subropes 14 a and 14 b which are coupled together using the coupling rope 18 a, as shown in FIG. 5 and described above.

As shown in FIG. 2, the core 12 has twenty-four subropes 14, which are arranged in a rectangular pattern following completion of the splicing procedure. In the region of the eye end termination 16, the coupling ropes 18 are arranged in three layers of four ropes each, which comprise an inner layer 38, an intermediate layer 40 and an outer layer 42, as shown in FIG. 3. Each coupling rope 18 is coupled to a pair of subropes 14, and thus one coupling rope serves for connecting two subropes. It will be appreciated that the number of coupling ropes 18 in each layer 38, 40 and 42 may be varied according to particular circumstances, including the diameter of the coupling ropes 18 and the desired finished dimensions of the eye end termination 16. However, each layer 38, 40 and 42 typically comprises four coupling ropes 18, each of which serves for coupling four pairs of subropes 14 in the rope core 12 together. This facilitates the balancing of forces in the eye end termination 16. This is because the rope 10 is torque balanced, and the rope core 12 comprises even numbers of S and Z lay subropes 14. The coupling ropes 18 each couple a pair of S or Z lay subropes 14 and are similarly oriented. Additionally, each layer 38, 40 and 42 of coupling ropes 18 comprises an even number (two each) of S and Z lay coupling ropes. This facilitates the balancing of forces in the eye end termination 16 in that an even number of S lay coupling ropes can be provided in each layer, and a corresponding even number of Z lay coupling ropes. Each pair of subropes 14 which is coupled together will typically be of the same lay (S or Z), and the coupling rope 18 will in each case also typically be of the same lay, to preserve the torque neutrality of the rope 10.

Returning to FIG. 5, the eye end termination 16 is formed around a bollard 44 and starts with the subropes 14 a and 14 b. These are separated from the first array 34 of the core 12 in a known fashion, typically by removing a part of the filter layer 13 and braided outer jacket 15, or by leaving these parts of the subropes exposed during manufacture. The coupling rope 18 a is positioned around the bollard 44 with the ends 26 a and 28 a laid either side of the bollard. The coupling rope 18 a is marked with splicing start points 46, and the subropes 14 a, 14 b extending from the standing rope 10 are laid next to the coupling rope 18 a and marked with their own splicing start points 48. The splicing markers 46 and 48 are lined up and the first portion 26 a of the coupling rope 18 a is spliced into the standing subrope 14 a and vice versa, using a butt splice. A butt splice is essentially two eye splices butted together in each direction from a central start point, which in this instance is the aligned splicing markers 46 and 48. The second portion 28 a of the coupling rope 18 a is then similarly butt spliced to the subrope 14 b, and the subropes 14 a, 14 b and the coupling rope 18 a are then connected as shown in the right hand side of FIG. 5. The length of the coupling ropes 18 is a function of the subrope 14 diameter, as a tucking pitch is used which is based on this. The number of tucks in the splice is the same regardless of the subrope breaking load. The number of tucks may typically be twenty-two, and a tucking pitch of three times subrope diameter employed.

The steps of FIG. 5 are repeated as necessary using the desired number of coupling ropes 18 for the layer 38, as shown in FIG. 3. In the illustrated embodiment, all three of the subropes 14 in the first radial array 34, together with five subropes from the second radial array 36 are coupled together to form the first layer 38. The intermediate layer 40 is then formed as shown in FIG. 6. A coupling rope 18 b of the intermediate layer 40 is shown in the left hand side of FIG. 6 being spliced to a pair 48 of subropes 14 c and 14 d of the second radial array of subropes 14. The process for the ropes in the intermediate layer 40 is the same as for the inner layer 38, but splice marks 46 and 48 are moved to account for the extra length due to the increased diameter of the intermediate layer 40. This is due to the coupling ropes 18 of the intermediate layer 40 being arranged over the ropes 18 of the inner layer 38. The outer layer 42 is then built up, also in a similar fashion. As with the intermediate layer 40, splice marks on the subropes 14 and coupling ropes 18 of the outer layer 42 are once again moved to account for the extra length due to the increased diameter of the outer layer 42. A braided cover (not shown) is then fitted over the splices, and is secured in position by tucking yarns of the cover into the cover plaits of the coupling ropes 18 and subropes 14. To finish, a coating of a two-part polyurethane material is applied to the eye end termination 16 (including the splices), in a similar fashion to that shown and described in relation to Fig. D, to provide abrasion resistance during handling.

Turning now to FIGS. 7, 8 and 9, there are shown side, plan and perspective views, respectively, of two ropes 100 and 200 coupled together. The rope 100 is also shown in FIG. 10, which is a view similar to that of the rope 10 in FIG. 1. Each rope 100, 200 comprises a core 112 (FIG. 10) having a plurality of multi-strand subropes 114, similar to that shown in Fig. A. The ropes 100 and 200 also have respective eye end terminations 116 and 216. The eye end terminations 116 and 216 have a plurality of loops or eyes, the loops being formed in accordance with a method of another embodiment of the present invention. Like components of the ropes 100, 200 with the rope 10 of FIGS. 1 to 6 share the same reference numerals incremented by 100 and 200, respectively. Each of the ropes 100 and 200 are assembled in a similar fashion. Reference will be made to the method of assembling the rope 100, but it will be understood that a similar method is employed in assembling the rope 200.

The eye end termination 116 of the rope 100 comprises a plurality of loops and, in the illustrated embodiment, comprises two loops 50 and 52. The eye end termination 216 of the rope 200 comprises similar such loops 250 and 252. Each loop 50, 52 and 250, 252 is formed according to the method described above in relation to FIGS. 1 to 6. Accordingly, only the significant differences between the methods will be described herein. The rope 100 is also shown in the cross-sectional views of FIGS. 11, 12 and 13 taken respectively in the direction of the arrows X′-X′, Y′-Y′ and Z′-Z′ of FIG. 10, which are similar to the views of the rope 10 in FIGS. 2 to 4.

Each of the loops 50 and 52 of the rope 100 are formed by coupling subropes 114 in the core 112 of the rope 100 together using multi-strand coupling ropes 188, according to the method described above. However, instead of forming an eye end termination having a single loop, the eye end termination 116 has the two separate loops 50 and 52. FIG. 10 shows the loop 50, which has an eye aperture 129. The separate loops 50, 52 are formed by arranging the coupling ropes 118 into two separate groups and coupling the ropes in the group together. The ropes in the groups are coupled together by applying one or more covers, which may comprise a filter layer and an outer braided cover or jacket (not shown), similar to the filter layer 4 and cover 5 shown in Fig. A. These are applied over the spliced regions 53 and separately around the coupling ropes in each of the groups forming the loops 50 and 52. FIG. 8 shows outer braided jackets 54 and 56 on the loops 50 and 52. Typically separate filter layers and covers will be applied over each loop 50, 52 and over the spliced region 53. A coating such as the polyurethane coating discussed above in relation to Fig. D is then applied to the spliced region 53 and the loops 50, 52. FIG. 12 shows one possible arrangement of the coupling ropes 118 in the separate groups which are subsequently arranged to form the loops 50, 52. It will be appreciated however that other arrangements are possible. Indeed and as described above, the rope 100 may comprise a different number of subropes 114 in its core 112 and thus a different number of coupling ropes 118.

Formation of the ropes 100 and 200 including two separate loops 50, 52 and 250, 252 provides a number of advantages. In particular, the two ropes 100 and 200 can be coupled together utilising a single connecting component which, in the illustrated embodiment, takes the form of a spool 58. The spool 58 is shown in more detail in the enlarged perspective and front views of FIGS. 14 and 15. The single spool 58 can be used in place of prior connecting assemblies comprising two separate spools, located in each eye end termination of two ropes to be coupled together and joined by a connecting chain, or indeed some other form of connecting component such as a relatively large and heavy H-link connector. This is made possible because the loops 50, 52 and 250, 252 of the ropes 100 and 200 can be coupled to the spool 58 in such a fashion that the forces exerted on the spool by the respective pairs of loops can be balanced. In particular, it will be noted that the two loops 50, 52 of the rope 100 are located axially inwardly of the two loops 250, 252 of the rope 200. This resists twisting of the spool 58 and thus separation of any of the loops 50, 52 or 250, 252 from the spool during use, by balancing shear forces on the spool 58 from the two ropes 100 and 200. In contrast, it would not be possible to couple two ropes (not shown) having eye end terminations with single loops together side by side on a spool, as the resultant forces would cause the spool to twist and there would be a risk of damage to the eye end terminations and/or separation of the terminations from the spool.

The spool 58 is shown in more detail in FIGS. 14 and 15. The spool 58 has main end flanges 60 and 62 defining respective axial ends of the spool. Further intermediate flanges 64 and 66 are provided spaced along a length of a hub 68 of the spool between the end flanges 60 and 62. The intermediate flange 64 is spaced axially from the end flange 60 so as to define a recess 70 which is shaped to receive a loop of one of the eye end terminations 116, 216 of the ropes 100 and 200, ideally in a snug fit. In the illustrated embodiment, the recess 70 receives the loop 250 of the rope 200 eye end termination 216.

The other intermediate flange 66 is similarly spaced with respect to the end flange 62 so as to define a recess 72 which, in this instance, receives the loop 252, again ideally in a snug fit. The flanges 60, 64 and 62, 66 act to prevent migration of the respective loops 250 and 252 along a length of the spool hub 68 during use.

The intermediate flanges 64 and 66 also define a central recess 74 therebetween for receiving further loops of the eye end terminations 116, 216. In the illustrated embodiment, the central recess 74 receives both loops 50 and 52 of the rope 100 eye end termination 116. Again, the flanges 64 and 66 are spaced such that the recess 74 receives the loops 50 and 52, ideally in a snug fit, and so that the flanges prevent migration of the loops along a length of the hub 68 during use.

It will be appreciated that the loops 50, 52 and 250, 252 may be differently oriented on the spool 58. For example, the loops may be spaced alternately along a length of the hub 68 so that one loop from each eye end termination 116, 216 is received in the central recess 74. Furthermore, it will be understood that the spool 68 may be arranged to have fewer or greater intermediate flanges and may indeed be provided without any intermediate flanges. Additionally, the eye end terminations 116, 216 of the ropes 100, 200 may have a different number of loops. For example, they may have an odd number of loops and may have three loops, or may have four loops. Where a rope has an eye end termination with an odd number of loops, it may be desirable that the other rope coupled to the spool have an even number of loops which can be fitted between the loops of the first rope. The spool may be constructed accordingly for providing a good fit with the loops of the ropes.

Various modifications may be made to the foregoing without departing from the spirit or scope of the present invention.

For example, the structure of the rope, in particular the rope core (comprising the plurality of subropes), may be constructed according to one of a number of different techniques, as will be understood by persons skilled in the art. Thus it will be understood that the principles of the present invention may apply to many different types of ropes, manufactured according to a number of different techniques. Indeed, the subropes in the rope core may comprise a plurality of strands formed from yarns (or fibres) which are twisted together; may comprise a plurality of strands formed from yarns (or fibres) which are braided together; and/or a combination of the two. Different arrays or layers of subropes in the core may be manufactured according to different techniques.

In another embodiment of the present invention, a method of forming an eye end termination on a rope, a rope and/or an eye end termination may be provided having one or more of the features of one or more of the embodiments described above and/or shown in the accompanying drawings. 

1. A method of forming an eye end termination on a rope having a core comprising a plurality of multi-strand subropes each of a first strength, the method comprising the step of: coupling a pair of subropes in the rope core together using a multi-strand coupling rope of second strength which is greater than said first strength, to thereby form at least part of an eye end termination; wherein the step of coupling the pair of subropes together comprises splicing a first portion of the coupling rope to one of the subropes in the pair of subropes, and splicing a second portion of the coupling rope to the other one of the subropes in the pair of subropes.
 2. A method of forming an eye end termination as claimed in claim 1, wherein the method is a method of forming an eye end termination on a rope in which the number of coupling ropes extending around a perimeter of and forming at least part of the eye end termination is less than the number of subropes in the rope core.
 3. A method of forming an eye end termination as claimed in claim 1, wherein the coupling of the pair of subropes together using the coupling rope involves forming a loop comprising the coupling rope and parts of the first and second subropes in the subrope pair to which the coupling rope is spliced, which loop forms at least part of the eye end termination.
 4. A method of forming an eye end termination as claimed in claim 1, wherein the method comprises the steps of: coupling a first pair of subropes in the rope core together using a first multi-strand coupling rope, to thereby form part of an eye end termination; and coupling at least one further pair of subropes in the rope core together using at least one further multi-strand coupling rope, to thereby form a further part of the eye end termination.
 5. A method of forming an eye end termination as claimed in claim 4, wherein the step of coupling the first pair of subropes together comprises splicing a first portion of the first coupling rope to one of the subropes in the first pair of subropes, and splicing a second portion of the first coupling rope to the other one of the subropes in the first pair of subropes.
 6. A method of forming an eye end termination as claimed in claim 5, wherein the step of coupling the at least one further pair of subropes together comprises splicing a first portion of the at least one further coupling rope to one of the subropes in the at least one further pair of subropes, and splicing a second portion of the at least one further coupling rope to the other one of the subropes in the at least one further pair of subropes.
 7. A method of forming an eye end termination as claimed in claim 1, comprising forming an eye end termination on a rope having a rope core comprising a first array of subropes and at least one further array of subropes, the or each said further array of subropes located radially outwardly of a preceding array.
 8. A method of forming an eye end termination as claimed in claim 1, comprising the steps of: coupling a pair of subropes in a first array of the rope core together using a first multi-strand coupling rope, to thereby form part of an eye end termination; and coupling a pair of subropes in at least one further array of the rope core together using at least one further multi-strand coupling rope, to thereby form a further part of the eye end termination.
 9. A method of forming an eye end termination as claimed in claim 8, wherein the step of coupling the pair of subropes in the first rope core array together comprises splicing a first portion of the first coupling rope to one of the subropes in said pair of subropes, and splicing a second portion of the first coupling rope to the other one of the subropes in said pair of subropes.
 10. A method of forming an eye end termination as claimed in claim 9, wherein the step of coupling the pair of subropes in the at least one further array comprises splicing a first portion of the at least one further coupling rope to one of the subropes in said pair of subropes, and splicing a second portion of the at least one further coupling rope to the other one of the subropes in said pair of subropes.
 11. A method of forming an eye end termination as claimed in claim 7, wherein one or more of the arrays of subropes in the rope core comprises a plurality of pairs of subropes, and the method comprises the steps of: coupling a first pair of subropes in at least one of the arrays of the rope core together using a first multi-strand coupling rope, to thereby form part of an eye end termination; and coupling at least one further pair of subropes in said array of the rope core together using at least one further multi-strand coupling rope, to thereby form a further part of the eye end termination.
 12. A method of forming an eye end termination as claimed in claim 11, wherein the step of coupling the first pair of subropes in said array together comprises splicing a first portion of the first coupling rope to one of the subropes in the first pair of subropes, and splicing a second portion of the first coupling rope to the other one of the subropes in the first pair of subropes.
 13. A method of forming an eye end termination as claimed in claim 12, wherein the step of coupling the at least one further pair of subropes in said array together comprises splicing a first portion of the at least one further coupling rope to one of the subropes in the at least one further pair of subropes, and splicing a second portion of the at least one further coupling rope to the other one of the subropes in the at least one further pair of subropes.
 14. A method of forming an eye end termination as claimed in claim 1, comprising coupling each subrope in the rope core to another subrope in the core using a coupling rope.
 15. A method of forming an eye end termination as claimed in claim 1, comprising coupling a plurality of pairs of subropes of the rope core together using respective coupling ropes, and arranging the coupling ropes to form overlapping rope layers of the eye end termination.
 16. A method of forming an eye end termination as claimed in claim 15, comprising coupling at least two pairs of subropes in the rope core together using respective coupling ropes and arranging said coupling ropes in a first layer; and coupling at least two further pairs of subropes in the rope core together using respective further coupling ropes and arranging said coupling ropes in a second layer located around the first layer.
 17. A method of forming an eye end termination as claimed in claim 1, wherein the method is a method of forming an eye end termination having at least two separate loops.
 18. A method of forming an eye end termination as claimed in claim 17, wherein the method comprises forming an eye end termination having an even number of loops.
 19. A method of forming an eye end termination as claimed in claim 17, wherein each loop of the eye end termination is formed by coupling a plurality of pairs of subropes in the rope core together using respective multi-strand coupling ropes.
 20. A method of forming an eye end termination as claimed in claim 17, wherein the method comprises the steps of: coupling at least one pair of subropes in the rope core together using a multi-strand coupling rope to thereby form at least part of a first loop of the eye end termination; and coupling at least one further pair of subropes in the rope core together using a multi-strand coupling rope to thereby form at least part of a further loop of the eye end termination, said further loop being separate from the first loop.
 21. A rope comprising a core having a plurality of multi-strand subropes and at least one eye end termination; wherein the eye end termination comprises at least one multi-strand coupling rope having a first portion spliced to one of a pair of subropes in the rope core and a second portion spliced to the other one of the subropes in the pair of subropes; and wherein the subropes are of a first strength and the coupling rope is of a second strength which is greater than said first strength.
 22. A rope as claimed in claim 21, wherein the coupling rope is of a second strength which is at least 1.5 times greater than a first strength of the subrope material.
 23. A rope as claimed in claim 21, wherein the coupling rope comprises a plurality of yarns, each coupling rope yarn being of a material having a tenacity which is at least about 1900 mN/tex.
 24. A rope as claimed in claim 21, wherein each subrope comprises a plurality of yarns, each subrope yarn being of a material having a tenacity which is no more than about 900 mN/tex.
 25. A rope as claimed in claim 21, wherein the eye end termination has at least two separate loops.
 26. A rope as claimed in claim 25, wherein each loop of the eye end termination comprises a plurality of pairs of core subropes coupled together using respective multi-strand coupling ropes. 